Lambda light 850 t5

[02GF74]

Codes 2-3-1 and 2-3-2, fuel mixture out of spec. Could you caused by intake of water vapour?

I'm unable to clear the fault codes.

Haynes manual states
- lead in A-2
- ignition on
- hold button for 5 sec, the LED should light up after 3 seconds but it doesn't.

Is there a way to reset the codes?

[richmac]

Hi,

Best guess from what you've described is that the rear O2 sensor got wet/ dislodged.

Some codes can be cleared by disconnecting the battery for 30 mins or so.

Best regards,

Rich.

[02GF74]

ok. battery just disconnected. now to wait 1/2 hour.

That didn't work. Any other ideas?

[nickm]

Originally Posted by 02GF74

ok. battery just disconnected. now to wait 1/2 hour.

That didn't work. Any other ideas?

It's generally a Vacuum leak. You can reset the system


Test Mode No. 1 (Erasing Codes)
1) Codes can be erased only after all DTCs have been
displayed and first DTC has been repeated at least once. To erase DTC,
turn ignition on. Press test button on Volvo diagnostic unit and hold
for more than 5 seconds. Wait for LED response.
2) Press button again and hold for more than 5 seconds. Turn
ignition off and on. Start engine. All DTCs will be erased and all
adaptive values reset.

[02GF74]

Didn't get round to trying that but there is more to this than I first thought.

The idle rpm has dropped slightly, was about 900, is now 850 but I notice when taking my foot off accelerator such as changing gear, the cars slows down a bit more than before.

Now here's the kicker, mpg has dropped significantly. On a gentle and steady motorway run I was getting 33 mpg, now it had dropped to just over 25mpg.

On the day the EM light came on, I did note the average mpg had dropped a bit iirc was around 32 but should have gone up have crept up due to a long motorway run. It dropped slightly due to the large number of miles done before resetting the trip computer.

The TC was reset due to the battery being disconnected, so now very few miles have been done so it is very clear the mpg is down.

[richmac]

When the Lambda light comes on, the ECU defaults to 'worst case' and increases the mixture to protect the engine. This will manifest itself in the symptoms you're experiencing although I don't know if that would affect engine braking.

Did you check your O2 sensor? The ECU uses the 2 sensors to help control the mixture.

[02GF74]

been reading bout how to test the sensor and also how inaccessible the plug is ....

I will try squirting a bit of WD40 to MAF plug in case water got in (although it should have dried out by now!) and same for the O2 sensors.

Also time to clean out the K&N air filter.

I ok repairing most stuff if I know what needs doing but not so great figuring out what is run in cases like this which could be one of several things....

[Luxobarge]

Originally Posted by 02GF74

Also time to clean out the K&N air filter.

Actually that's one of the first things i'd have done, if you've been through deep water you could have sucked up water into the intake which would soak the filter, and cause all sorts of running issues. Let us know what state the filter and associated pipework is in, I'd be interested to know. If there are indeed any signs of the filter getting wet, i'd be strongly tempted to replace it.

[02GF74]

Just looked inside and no sign of water. Bear in mind the intake is about 2 ft from the ground, I doubt the water was more than 6 inches.

My best guess at the moment is the water hit the O2 sensor and the rapid change of temperature broke it.

Car is 30 years old this year, 160k miles and still on original exhaust and O2 sensors, the latter I read last up to 100 k miles.

I'll have look underneath over the weekend but I expect the exhaust pipe to crumble when trying to remove the sensor.

[nickm]

The times I have got these codes it was always a vacuum leak .
PCV hose on the intake
The boost return on the intake
The Manifold vacuum tree o ring
And the Cruise control.

Originally Posted by 02GF74

Just looked inside and no sign of water. Bear in mind the intake is about 2 ft from the ground, I doubt the water was more than 6 inches.

My best guess at the moment is the water hit the O2 sensor and the rapid change of temperature broke it.

Car is 30 years old this year, 160k miles and still on original exhaust and O2 sensors, the latter I read last up to 100 k miles.

I'll have look underneath over the weekend but I expect the exhaust pipe to crumble when trying to remove the sensor.